Electroless metal plating with foam



United States Patent 3,300,335 ELECTROLESS METAL PLATING WITH FOAM JackW. Horvath, Angleton, and Arthur C. Doumas, Lake Jackson, Tex.,assignors to The Dow Chemical Company, Midland, Mich, a corporation ofDelaware No Drawing. Filed Nov. 20, 1963, Ser. No. 325,127 9 Claims.(Cl. 117130) This invention relates to an improved method forelectroless plating of various materials, and more particularly to anelectroless method utilizing a foamed plating solution.

Known methods of electroless plating usually require large excessamounts of solution per unit area of surface to be plated. For instance,when it is desired to plate the interior surface of a large vessel, thevessel usually must be filled with solution. The volume of solutionrequired to fill the vessel is generally greatly in excess of the amountof solution required to give the desired plate, Because the life of mostelectroless plating solutions is usually not very long, the use ofsubstantial excess amounts of solution can be extremely wasteful.

We have discovered a method wherein electroless plating may beaccomplished employing a fraction of the volume of plating solutionheretofore required. In accordance with our method, a quantity of afoaming agent, preferably from about 0.01 to about 1.0 percent by volumeis added to the desired plating solution and a gas is then passedthrough the solution to become admixed with said solution thereby toform a foam. The foam is then applied to the basis material to beplated, spent solution and spent foam being removed after the desiredplating is accomplished. In certain situations, such as plating largesurface areas and the like, it may be desirable to continuously add newfoam to the plating surface and withdraw spent solution and residualfoam.

Suitable foaming agents are generally those which are not reactive withthe plating metal or the basis material receiving the plate and do notform a precipitate with the bath. Water dispersa-ble soaps, commonhousehold detergents, and many other foama ble surfactants are generallysatisfactory. Examples of some suitable foaming agents, to which thepresent invention is not limited, are sodium lauryl sulfate, organicsalts of lauryl sulfate, sodium lauryl ethoxylated sulfate, nonyl phenolethylene oxide adduct, fatty alcohol sodium sulfate, sodium dodecyldiphenyl oxide disulfonate, lauric diethanolamide, ethoxylated tridecylalcohol, and the like.

Examples of some of the commercially available foaming agents, useful inthe present invention are:

Trade Name Manufacturer Class and Formula Acetoquat CTAB Aceto ChemicalCompany Cetyl trimethyl ammonium bonnide.

CTAC do Cetyl trimethyl ammonium chloride.

ODAO Cctyl dimethyl benzylammonium chloride. Acetoquat CPO Cetylpyridinium chloride.

CPB. do Cetyl pyridinium bromide. Aeidol 25A Onyx Chemical Corporation.Alkyl dimethyl amine acetate. Aerosol C-61 American Cyanamid Company. Anethanolated allgylguanidine amine complex. Alamine 4, 5, 6, 7, 11, 15,21, 26, 1126, 33 General Mills, Inc Primary fatty amines, RNHz. Alamine204, 205, 206, 207, 215, 221, H226". .do Secondary fatty amines, RQNH-Aliquat 204, 205, 206, 207, 215, 221, H226 ..do N-dllatty dimethylquaternary ammonium Alkanol S Flakes. Amine E. I. du Pont de Nemours &Co Geigy Chemical Corporation Ony: Chemical Corporation o chlorides.

Sodium tetrahydronaphthalene sulfonate. Hetero cyclic tertiary amine,

Stearyl dimethyl benzyl annnonium chloride.

Cetyl dimethyl amine oxide. Cetyl dimethyl ethyl ammonium bromide.

Arquad 2HT-75 Arquad 28-75 Benax 2A1 Catanac SN Cerfak 1300 Comperlan lComperlan LM Comperlan LP Comperlan RM Armour dz Company o The DowChemical Company American Cyauamid Company 0. L. King & Company FallekProducts Company Di-stearyl dimethyl ammonium chloride.

Di-soya dimethyl ammonium chloride.

Na Dodecyldiphenyl oxide disulfonate oxyethylated alkylphenols.

Stcaramido propyl di-methyl-B-hydroxy ethyl ammonium nitrate.

Fatty amido diarnine.

Alkyl polyoxyethylene thioether.

Coco fatty acid monoethanolamide.

Laurie acid monoethanolamide.

Laurie acid isopropanolamide.

Fatty acid ethanolamide.

Coco fatty acid polydiethanolamide.

Comperlan PD DBI O me Or anics Incorporated N-dodccyl benzyl N NNtrimethyl ammonium chloride.

Dehyquart C Diam 21 Dichloran Dowfax 9N series Monamid l-L Monamid -M.

Fallek Products Company General Mills, Inc Fine Organics, Inc.

lhe Dow Chemical Company Fallek Products Company Hooker Chemical CorpMon: Industries, Inc

Nalcamine G-l2 Nalco Chemical Co Sodium Vinyl Benzene Sulfona e Surfynol61 Surtynol 82.

Rohm & Haas Co Air Reduction Chemical Co Tergitol 08 Union CarbideChemicals Co Lauryl pyridinium chloride. N-fatty propylene diamine.Alkyl dimethyl diehlorobenzyl ammonium Trade Name Manufacturer Class andFormula Tergitol Ell .do

Wetting Agent F-126 acids, principally, perfiuoroeaprylie acid.

Gases appropriate for use in foaming the plating bath in accordance withthe present invention are those which are not generally reactive withthe plate metal, the material receiving the plate, or the plating bath.Usually, the relatively non-oxidizing gases such as hydrogen, carbondioxide, nitrogen, the noble gases and, under most conditions air, arepreferred.

Foaming is preferably accomplished by bubbling a gas, as describedabove, through the plating bath. Gas may be introduced to the bath byany suitable means, a sparge tube being one appropriate method. Otherknown means of foaming or frothing may be employed in addition to or inplace of the preferred gas-foaming method, if desired.

Materials appropriately plated by the method of the present inventionare those which are capable of being plated by electroless platingmethods. Typical of such basis materials, but to which the presentinvention is not limited, are: metals, plastics, glass, quartz, wood,silicon carbide, porcelain, graphite, refractory materials, and thelike.

Within the scope of the method of the present invention is included theuse of any metal ion such as, for example, arsenic, cadmium, copper,gold, lead, nickel, silver, tin, rhodium, and a palladium, in anysuitable electroless plating solution. The metal ion may be reduced byimmersion plating in which the surface being plated is the reducingagent, or the metal ion may be reduced by a chemical reducing agent suchas, forexample, sodium hypophosphite, formaldehyde, Rochelle salt,hydrazine, or an acid.

The following examples are set forth to further illustrate, and are notto be construed to limit, the present invention.

Example ].An aqueous plating bath was prepared having the followingcomposition:

Grams per liter Sodium hypophosphite 20 Basic nickel carbonateHydrofluoric acid (70% HF) 6 Citric acid 5.5 Ammonium acid fluorideNonyl phenol ethylene oxide adduct 5 Steel coupons of dimensions of 2%inches by 4 inches by A inch and having'the nominal designation SAE 1020were cleaned and pickled in percent HCl solution, then rinsed and dried.

Two liters of the above solution were poured into a container havingdimensions 4 inches by 4 inches by 60 inches in height the solutionbeing maintained at a temperature of from about 180 to 185 degreesFahrenheit. Four of the steel coupons were suspended in the containerabove the solution. Air Was bubbled int-o the solution to produce a foamhaving sufficient height to cover the coupons.

After exposure of the coupons to the foam for about one hour, thecoupons were removed from the container, rinsed, and examined.Asatisfactory coating of nickel had been deposited on each of thecoupons.

Example 2.An aqueous plating bath was prepared having the followingcompositions:

Grams per liter Sodium hypophosphite 27 Nickel chloride 10 Sodiumsuccinate 16 Lead chloride 0.004 Nonyl phenol ethylene oxide adduct 5Coupons of SAE 1020 steel having the dimensions 1 inch by 4 inches by,--inch were prepared as in Example 1 and placed in a long glass tubehaving a diameter of 1% inches. Foam was generated by bubbling hot airthrough the plating solution and passed through the tube. Temperature ofthe solution and foam varied from about 205 to about 210 degreesFahrenheit. Solution was passed through the tube for a period of onehour and forty-five minutes.

After exposure to the foam for the above period, the coupons wereremoved from the glass tube, rinsed and examined. A satisfactory coatingof nickel had been deposited on each coupon.

Example 3.- An aqueous plating bath was prepared having the followingcomposition:

Grams per liter Sodium hypophosphite 27 Nickel chloride 20 Aminoaceticacid 15 Tetrasodium salt of ethylene diamine tetra acetic acid 8 Leadchloride 0.004 Sodium dodecyl diphenyl oxide disulfonate 5 Coupons ofSAE 1020 steel of the size used in Example 2 were degreased, pickled,rinsed with a 2 percent solution of sodium salt of ethylene diaminetetraacetic acid, and dried. Employing substantially the method andsolution of Example 2, except that nitrogen was the foaming gas, thecoupons were exposed to foam individually in separate runs. Theconditions were varied and the results tabulated as follows:

TABLE Trial N 0. Duration, Temperature, Thicknc ss,

Minutes Degrees F. Inches X10 Observation of the coupons after thecoatings indicated that the nickel plating was uniform and free of pinholes and satisfactory in all respects.

Example 4.An 8-inch length of admiralty brass tube was degreased,pickled, and rinsed with a tetrasodium ethylene diamine tetraacetic acidsolution. The length of brass tube was then immersed in an acidpalladium chloride solution and rinsed thoroughly. Employing the methodsubstantially as outlined in Example 2 and the bath of Example 3, foamat 180 degrees Fahrenheit was run through the tube for 2 /2 hours. Theinside of the tube received a uniformly bright, electroless nickelcoating 2.04 mils thick. The plate was uniform and free of pin holes.

Example 5.A graphite rod /2-inch in diameter and 4 inches long was wasdegreased with perchloroethylene, dipped in a stannous chloridesolution, dipped in a palladium chloride solution, and thoroughlyrinsed. Using substantially the method outline in Example 2 and thesolution of Example 3, the graphite rod was exposed to plating foam,said foam having a temperature of about 180 degrees Fahrenheit, for atime of about /2-hour. A smooth, pin hole-free nickel coating 0.4 milthick was deposited on the graphite rod.

Example 6.In substantially the same manner described above, arsenic,cadmium, copper, gold, lead, silver, tin, rhodium and palladium may beplated on suitable basis materials byernploying a conventional andappropriate electroless plating solution containing from about 0.01 toabout 1.0 percent by volume of a foaming agent.

Various modifications may be made in the present invention withoutdeparting from the spirit or scope thereof, and it is to be understoodthat we limit ourselves only as defined in the appended claims.

We claim:

1. In a method wherein a basis material is plated with metal bycontacting said basis material with an electroless plating solution, theimprovement which comprises adding to said plating solution an amount ofa foaming agent sufficient to permit foaming, foaming said solution,contacting the basis material with said foam, and removing spentsolution from contact with the basis material.

2. In a method wherein a basis material is plated with metal bycontacting said basis material with an electroless plating solution, theimprovement which comprises adding to said plating solution from about0.01 to about 1.0 percent by volume of a foaming agent, foaming saidsolution, contacting the basis material with said foam, and removingspent solution from contact with the basis material.

3. In a method wherein a basis material is plated with metal bycontacting said basis material with an electroless plating solution, theimprovement which comprises adding to said plating solution an amount ofa foaming agent suificient to permit foaming, passing gas through saidsolution thereby to form a foam, contacting the basis material with saidfoam, and removing spent solution from contact with the basis material.

4. In a method wherein a basis material is plated with metal bycontacting said basis material with an electroless plating solution, theimprovement which comprises adding to said plating solution from about0.01 to about 1.0 percent by volume of a foaming agent, passing gasthrough said solution, thereby to form a foam, contacting the basismaterial with said foam, and removing spent solution from contact withthe basis material.

5. In a method wherein a basis material is plated with nickel bycontacting said basis material with an electroless nickel platingsolution, the improvement which comprises adding to said nickel platingsolution from about 0.01 to about 1.0 percent by volume of a foamingagent, passing gas through said solution, thereby to form a foam,contacting the basis material with said foam, and removing spentsolution from contact with the plated surface.

6. In a method wherein a steel surface is plated with nickel bycontacting said steel surface with an electroless nickel platingsolution, the improvement which comprises adding to said nickel solutionfrom about 0.01 to about 1.0 percent by volume of nonyl phenol ethyleneoxide adduct, passing air through said solution, thereby to form a foam,contacting the steel surface with said foam, and removing spent solutionfrom contact with the plated surface.

7. In a method wherein a steel surface is plated with nickel bycontacting said steel surface with an electroless nickel platingsolution, the improvement which comprises adding to said nickel solutionfrom about 0.01 to about 1.0 percent by volume of sodium do-decyl diphenyl oxide disulfonate, passing :air through said solution, thereby toform a foam, contacting the steel surface with said foam, and removingspent solution from contact with the plated surface.

8. In a method wherein a brass surface is plated with nickel bycontacting said brass surface with an electroless nickel platingsolution, the improvement which comprises adding to said nickel solutionfrom about 0.01 to about 1.0 percent by volume of nonyl phenol ethyleneoxide adduct, passing air through said solution, thereby to form a foam,contacting the brass surface with said foam, and removing spent solutionfrom contact with the plated surface.

9. In a method wherein a graphite surface is plated with nickel bycontacting said graphite surface with an electroless nickel platingsolution, the improvement which comprises adding to said nickel solutionfrom about 0.01 to about 1.0 percent by volume of nonyl phenol ethyleneoxide adduct, passing air through said solution, thereby to form a foam,contacting the graphite surface with said foam, and removing spentsolution from contact with the plated surface.

ALFRED L. LEAVITT, Primary Examiner.

R. S. KENDALL, Assistant Examiner.

1. IN A METHOD WHEREIN A BASIS MATERIAL IS PLATED WITH METAL BYCONTACTING SAID BASIS MATERIAL WITH AN ELECTROLESS PLATING SOLUTION, THEIMPROVEMENT WHICH COMPRISES ADDING TO SAID PLATING SOLUTION AN AMOUNT OFA FOAMING AGENT SUFFICIENT TO PERMIT FOAMING, FOAMING SAID SOLUTION,CONTACTING THE BASIS MATERIAL WITH SAID FOAM, AND REMOVING SPENTSOLUTION FROM CONTACT WITH THE BASIS MATERIAL.